Abstract
During regular firing of "small" motor units, activated during weak voluntary contraction of the human soleus muscle, thick efferent fibers of n. tibialis were stimulated (a small M response was evoked, in which the small units did not participate). Peristimulus histograms of potentials of single motor units were constructed and the effect of stimulation on interspike interval duration was analyzed. The firing rate of the motor units was 4.5–7.6 spikes/sec. Stimulation of the nerve led to a sharp decrease in probability of their discharge or even complete temporary cessation of firing, i.e., it had a well marked inhibitory effect (lasting 10–20 msec). The latent period of inhibition (35–40 msec) was only a little longer than the latent period of the monosynaptic reflex of the soleus muscle. The effect of an inhibitory volley on duration of the interspike interval of the motor units depended on the time when the volley arrived during the interval. Lengthening of the interval was observed only if the inhibitory volley arrived in the second half or at the end of the interval. It is concluded that inhibition of firing of small motor units is due to Renshaw cells, activated on stimulation of axons of large motoneurons. The efficiency of a short (compared with the duration of the interspike interval) inhibitory volley reaching a motoneuron firing at low frequency characteristic of its adequate activation, is discussed.
Similar content being viewed by others
Literature cited
L. P. Kudina, "Investigation of reciprocal inhibition on firing human motor units," Neirofiziologiya,10, No. 6, 626 (1978).
R. S. Person and G. V. Kozhina, "Investigation of the silent period by the post-stimulus histogram method," Neirofiziologiya,10, No. 2, 77 (1978).
B. Bussel and E. Pierrot-Deseilligny, "Inhibition of human motoneurones, probably of Renshaw origin, elicited by an orthodromic motor discharge," J. Physiol. (London),269, No. 2, 319 (1977).
A. K. Datta and J. A. Stephens, "The stimulus locked interval histogram: a method that may allow investigation of Renshaw inhibition in man," J. Physiol. (London),293, No. 8, P16 (1979).
J. C. Eccles, P. Fatt, and K. Koketsu, "Cholinergic and inhibitory synapses in a pathway from motor axon collaterals to motoneurons," J. Physiol. (London),126, No. 3, 524 (1954).
J. C. Eccles, R. M. Eccles, A. Iggo, and M. Ito, "Distribution of recurrent inhibition among motoneurones," J. Physiol. (London),159, No. 3, 479 (1961).
P. H. Ellaway and P. R. Murphy, "A comparison of the recurrent inhibition of α- and γ-motoneurones in the cat," J. Physiol. (London),315, 43 (1981).
H. Hultborn and E. Pierrot-Deseilligny, "Changes in recurrent inhibition during voluntary soleus contractions in man studied by an H-reflex technique," J. Physiol. (London), 297, 229 (1979).
F. A. Kirkwood, T. A. Sears, and R. H. Westgaard, "Recurrent inhibition of external (inspiratory) intercostal motoneurones," Neurosci. Lett.,19, Suppl. No. 5, 226 (1980).
E. Pierrot-Deseilligny and B. Bussel, "Evidence for recurrent inhibition by motoneurones in human subjects," Brain Res.,88, No. 1, 105 (1975).
E. Pierrot-Deseilligny, C. Morin, R. Katz, and B. Bussel, "Influence of voluntary movement and posture on recurrent inhibition in human subjects," Brain Res.,124, No. 3, 427 (1977).
B. T. Shahani and R. R. Young, "Studies of the normal human silent period," in: New Developments of Electromyography and Clinical Neurophysiology, Vol. 3, Karger, Basel (1973), pp. 589–602.
J. L. Veale and S. Rees, "Renshaw cell activity in man," J. Neurol. Neurosurg. Psychiat.,36, No. 4, 674 (1973).
Additional information
Institute for Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 88–96, January–February, 1984.
Rights and permissions
About this article
Cite this article
Kudina, L.P., Pantseva, R.É. Detection and analysis of recurrent inhibition of firing motoneurons in man. Neurophysiology 16, 80–87 (1984). https://doi.org/10.1007/BF01052831
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01052831